Process for coating, impregnating, or alloying metals and other materials with aluminum and aluminum alloys



WALTER srn'rn,

"formed as well above the impre Patented June 3, 1930 UNITED STATES PATENT omcaor m'rmroon, ENGLAND, ASBIGNOB 'ro 'rrm mu. oonm,-nmrrnn, or LONDON, ENGLAND 2300138 103 OOATING, mBEGNATING, OR ALLOY ING METALS AND OTHER- KATI- BIALS WITH ALUKINUI AND ALUMINUM ALLOYS llo Drawing. Application fled Iaroh 8 1887, Serial 1T0. 172,207, and in Great Britain larch I'l, 1986. t

This invention relates to an improved'process for impregnating metals and other suitable materials with aluminum and aluminum alloys, rimarily for the urpose of rendering oorrodi le metals and ot or materials incorrodible when exposed to high temperatures.

It has been previously been proposed as a preliminary step to coating with aluminum or aluminum allo to coat "iron,..steel and other metals with tin, zinc, or an easily fusible metal and then to immerse the preliminary coated metal into a bath of molten aluminum or aluminum alloy with the object of superimposing a coating of aluminum or aluminum alloy on the surface of the foundation metal.

The-object of the present invention is to obtain more readily a thorough and effective impregnation into the surface of the foundation material. A coatin as distinct from a modified surface'of the foundation material due to impregnation, may or may not be ated surface. Generally speaking, for e purpose of protection against corrosion and the eflfects of high temperatures .there is no advantage in having a distinct coating of alumimun since the thorough impregnation obtained according to this invention secures adequate protection and moreover the properties or characteristics of the foundation metal are substantially unaltered.

According to this invention an article or object of metal or other material suitable therefor, is given a coating of cadmium, whereupon the coated article or object is treated with aluminum or an alloy of aluminum.

The coating of cadmium is preferably made as thin as possiblecom atible with a sound envelope and may be e ected by electrolytic deposition.

The treatment with aluminum or alloy thereof differs in accordance with the result desired.

By one methodthe article to which a coating as aforesaid has been given is immersed in molten aluminum or ahminuniplloy.

According to the basic iiietaiigareated. the time of immersion and thetemfie 'fetfure of the bath, the basic metal will become impregnated or alloyed with the aluminum or alumi-- num alloy, while there will be at the surface of the article a coating thereof.

When treating ferrous metals the bath temperature may be from 700 C. to 960. C. according to the type of finish required. When the result desired is obtained, it is withdrawn, any surplus metal removed, and the article allowed to cool naturall ing atmosphere, or may e quenched or treated such other manner as may be desired to obtain specific characteristics. Large articles ma'y be re-heated to prevent unnecessa cooling 0 the molten bath.

y this method mild steel articles to thick and treated at 800 C.-900 C. have been found to obtain a coatin of aluminum eqpal to..68 ozs. per square oot of surface a man immersion of one minute; of this coating approximately .26 ozs. per square foot is as metallic aluminum at the surface and .42 ozs. per square foot is alloyed with the steel below the surface.

Copper and copper alloys when similarly treated readily alloy-at the surface with the or in a non-oxidi zaluminum or aluminum alloy used. Care must be taken that the temperature at whichthey are treated does not exceed the melting point of the basic metal.

By another method an article e. g. of iron or steel, impregnated with cadmium as afore said is placed in a closed container together with powdered aluminum or aluminum alloy (alone or in combination with other metals or salts); the article need not be brought into contact with the powder itself but may be so arranged that the vapours gen-v erated from the powder come into intimate contact with the said articles. The container is then subjected to the required temperature and for the time necessary to give the desired result. Articles may be treated in this manner at from 650 C. to 1000 C. for half an hour or longer according to the basic metal, size of article and thedepth of penetration desired.

It will readily be understood that the invention is applicable to all articles or objects to which a coating of cadmium can be applied although of course the depth to which the aluminum or aluminum alloy can penetrate depends on the substance surfaced with cadmium. As cadmium can be deposited on plumbago it will be seen that a variety of materials can be so coated.

What I claim is 1. A process of impregnating a foundation article with a surface alloy of a substance comprising aluminum, which consists in first treating the article with cadmium and then treating the article with a substance comprising aluminum, the second treatment being carried out at a temperature below 900 C.

2. A process of impregnating a foundation article with surface allo of a substance comprising aluminum, which consists in first treating the article with cadmium and then treating the article with a molten substance comprising aluminum at a temperature between 700 C. and 900 C.

In testimony that I claim the foregoing as my invention I have signed my name this eighth day of Februar 1927.

ALTER SMITH. 

